In this study, we investigated the melting and crystallization behavior of polyhedral oligomeric silsesquioxane (POSS)-capped poly(epsilon-caprolactone) PCL with various lengths of PCL chains by means of X-ray diffraction and differential scanning calorimetry. This organic-inorganic macromolecule possesses a tadpole-like structure in which the bulky POSS cage is the "head" whereas PCL chain the "tail". The novel organic-inorganic association result in the significant alterations in the melting and crystallization behavior of PCL. The POSS-terminated PCL displayed the enhanced equilibrium melting points compared to the control PCL. Both the overall crystallization rate and the spherulitic growth rate of the POSS-terminated PCLs increased with increasing the concentration of POSS (or with decreasing length of PCL chain in the hybrids). The analysis of Avrami equation shows that the crystallization of the POSS-terminated PCL preferentially followed the mechanism of spherulitic growth with instantaneous nuclei. It is found that the folding free energy of surface for the POSS-terminated PCLs decreased with increasing the concentration of POSS. It is found that the folding free energy of surface for the POSS-terminated PCLs decreased with increasing the concentration of POSS. (c) 2007 Wiley Periodicals, Inc.